A first incursion into the 3D structure of natural convection of air in a differentially heated cubic cavity, from accurate numerical solutions

Accurate solutions to the equations governing the natural convection of air in a cubic cavity, thermally driven on two vertically opposite faces, are given for Rayleigh number values up to 107. These solutions are obtained with a pseudo-spectral Chebyshev algorithm based on the projection–diffusion method with a spatial resolution supplied by polynomial expansions, which go up to 111 × 111 × 111. The solutions are believed to be accurate—better than (0.03, 0.05)% in relative global error for the corresponding Rayleigh number (Ra) range (103, 107). This clearly indicates a non monotonic evolution of the flow structure as Ra increases.